This invention relates to controlling the input power and torque to a multi-speed transmission in a powertrain.
Powertrains generally consist of an engine and a transmission. The transmission has a torque converter and a planetary gear arrangement which includes a plurality of torque transmitting mechanisms in the form of both rotating and stationary clutches and band brakes. Each of these elements as well as the shafts in the transmission have a maximum torque capacity which, if exceeded, may be detrimental to the operation of the powertrain. The torque converter has a stall torque point at which the maximum torque capacity is reached. Generally the engine and transmission are matched such that the engine output torque and the converter stall torque are compatible such that the maximum torque limit of the transmission input shaft is not surpassed.
It is an object of the present invention to provide an improved torque and power control for a powertrain.
In one aspect of the present invention, an electronically controlled powertrain automatically limits the engine torque and power output within the ratings of the transmission. In another aspect of the present invention, the transmission controller contains the available transmission ratings for the transmission family to which it belongs including vocation and transmission range with and without the engagement of the torque converter clutch. In yet another aspect of the present invention, the transmission controller has the ability to provide different ratings for each transmission range, including reverse.
In still another aspect of the present invention, the transmission controller has five determiners for the engine torque limit including the transmission input torque, the transmission output torque, the transmission input power, the transmission turbine torque, and the torque converter slip speed limit. In a further aspect of the present invention, the controller contains values for the torque converter multiplication ratio and the torque converter K factors for each available torque converter model. In yet a further aspect of the present invention, an engine torque versus engine speed map is determined from the design and operating factors for each transmission gear ratio, with and without the engagement of the torque converter clutch, and the controller prohibits powertrain operation outside of the limits set by the map.